ON a residential
street corner on the outskirts of Singapore's red-light district of Geylang,
a van pulls up beside two women in the evening dusk, both dressed in revealing
blouses and hip-hugging skirts.

Moments later, 27-year-old Ming opens the van's door and disappears.
Her friend, 30-year-old Yeh, waits for another customer. Both are tourists
visiting from mainland China, and both are the vanguard of a new trend
in the oldest profession.

Prostitution is expanding from red-light urban districts into the leafy
suburbs, propelled mostly by mainland Chinese women on tourist visas and
fuelling a growing underground sex industry in a country known for prudish
laws and orderly living.

The trend follows a blossoming in ties between Singapore and China,
nourished on ethnic bonds, and is provoking a groundswell of public criticism
as prostitution spills out of legal and tightly regulated brothels.

Adding to the assault on Singapore's reputation as a strait-laced, strictly
controlled society is a US State Department report this year that said
the wealthy city state had a "significant" trafficking problem
involving women and children.

Singapore's government refuted the report, which put the Southeast Asian
island on par with Cambodia, China and Indonesia as "countries that
do not fully comply with the minimum standards" to eliminate trafficking
of women and girls for sex.

The focus on sex-for-hire in Singapore, whose ardour has been cast in
some doubt by a record-low fertility rate, has been further sharpened by
a new book "Invisible Trade" on a thriving world of high-class
prostitution in Singapore.

"People generally have this perception that Singapore is a squeaky
clean, prim and proper kind of place so they tend to be very surprised
when they find out that there is a thriving escort industry here,"
the book's author, Gerrie Lim, told Reuters.

"ROAMING NIGHTINGALES"

Singapore's Chinese-language media has branded the new wave of prostitutes
from China as "roaming nightingales" or "liuying" in
the Mandarin dialect, an analogy to birds known for singing at night. Newspapers
report cases of worried housewives escorting their husbands home from work
to prevent temptation.

In a report titled "China hookers are now in your neighbourhood",
the Straits Times newspaper thrust the issue into public debate
in July, describing prostitutes who single out elderly men in residential
areas.

The report touched a raw nerve. Some alarmed residents urged their leaders
to raise the issue with China.

"Bilateral ties with China are no doubt important but we should
not compromise our social values by allowing the prostitution problem to
get out of hand," wrote Tang Li Shan in one of a series of complaints
to local media.

Prostitution in Singapore is legal in several red-light districts where
Indonesian, Malaysian, Thai, Indian and Chinese women ply their trade in
brothels, karaoke lounges and massage parlours. Sex workers must carry
a health card and submit to medical checks. But soliciting for sex on the
street is illegal.

By far the biggest source of new sex workers is China, where an industrial
boom has triggered rural unemployment and a range of vices -- from prostitution
to human trafficking.

Singapore, whose population is Asia's third-wealthiest and 77 percent
ethnic Chinese, is a natural magnet.

Hoping to tap the new wealth of Chinese travellers, Singapore relaxed
immigration rules in January, doubling the days Chinese can stay to 30
and allowing more tour agencies to obtain visas.

The impact was immediate. Mainland Chinese were Singapore's fastest-growing
source of tourists from January to June. In the same period, the number
of foreign sex workers arrested shot up 50 percent, police data show. Most
of the women were from China.

"It's my first time here," explains Yeh, an affable, soft-spoken
women who looks about 5 years beyond her age. "I've stayed for about
20 days." She says she earns about S$300 each day. "I will have
to leave when my social visit pass expires."

PUBLIC BACKLASH

The lure to work Singapore's streets is strong. The island's annual
per capita income of about $21,000 dwarfs China's by about 25 times, and
Chinese prostitutes charge S$30 to S$100 for a tryst -- far below the S$100
to S$200 in most brothels.

Human rights activists caution that a public backlash could single out
mainland Chinese women who themselves are victims.

"When these women are arrested, it is important to ask if they
should be treated as victims or as criminals," said Edward Job, president
of One Hope Center, a non-governmental organisation that helps prostitutes
get out of the trade.

"Those who are forced into prostitution look to Singapore as the
land of milk and honey. They borrow money to come here in hope of decent
work but only to find themselves landing in debt and in prostitution,"
he said.

The US State Department's annual report on human trafficking, issued
in June, said Singapore did not consider it had a major problem in sex
trafficking and criticised it for lacking a plan to deal with the issue.

It reported seven cases of alleged forced prostitution in 2003 and two
convictions. Singapore's government said only two of 18 reports of forced
prostitution in 2002 and 2003 were substantiated, describing them as "very
rare".